code: def sending_headers(self):
      return {
          TRACE_HEADER: self.trace_id,
      }
  
imports: import argparse
  import sys
  import threading
  import uuid
  import pyarrow
  import pyarrow.flight
label_desc: Use image node_id 2 for calling the TracingServerMiddleware obj's underlying member method code with example usage: obj.sending_headers() and returns: dict